DistanceSensor (ultrasonic) in Raspberry Pi - Mini Project: Build & Apply

DistanceSensor (ultrasonic) with Raspberry Pi

📖 Scenario: You have a Raspberry Pi connected to an ultrasonic distance sensor. This sensor can measure how far an object is by sending sound waves and timing how long they take to bounce back.We want to write a simple program that reads the distance from the sensor and shows it on the screen.

🎯 Goal: Build a Python program that reads distance values from an ultrasonic sensor connected to the Raspberry Pi and prints the distance in centimeters.

📋 What You'll Learn

Create variables for the sensor pins

Set up the GPIO pins for input and output

Write code to send a pulse and measure the echo time

Calculate the distance from the echo time

Print the distance in centimeters

💡 Why This Matters

🌍 Real World

Ultrasonic sensors are used in robots, parking sensors, and obstacle detection to measure how far objects are.

💼 Career

Understanding how to read sensors and control hardware with code is important for jobs in robotics, embedded systems, and IoT development.

1

Set up GPIO pins for the ultrasonic sensor

Import the RPi.GPIO module as GPIO and the time module. Then create two variables called TRIG and ECHO and set them to 23 and 24 respectively. Finally, set the GPIO mode to GPIO.BCM.

Raspberry Pi

# Import modules and set pins
# Your code here

Need a hint?

Use import to bring in modules. Assign numbers 23 and 24 to TRIG and ECHO. Use GPIO.setmode(GPIO.BCM) to set pin numbering.

2

Configure GPIO pins for output and input

Use GPIO.setup to set the TRIG pin as an output and the ECHO pin as an input.

Raspberry Pi

import RPi.GPIO as GPIO
import time

TRIG = 23
ECHO = 24

GPIO.setmode(GPIO.BCM)
# Set TRIG as output and ECHO as input
# Your code here

Need a hint?

Use GPIO.setup(pin, GPIO.OUT) for output pins and GPIO.setup(pin, GPIO.IN) for input pins.

3

Send pulse and measure echo time

Write code to send a 10 microsecond pulse on the TRIG pin. Then use a while loop to wait until the ECHO pin goes high and record the start time. Use another while loop to wait until the ECHO pin goes low and record the end time. Calculate the pulse duration as end - start.

Raspberry Pi

import RPi.GPIO as GPIO
import time

TRIG = 23
ECHO = 24

GPIO.setmode(GPIO.BCM)
GPIO.setup(TRIG, GPIO.OUT)
GPIO.setup(ECHO, GPIO.IN)

# Send pulse and measure echo time
# Your code here

Need a hint?

Set TRIG low, wait, then high for 10 microseconds, then low again. Use loops to detect when ECHO changes state and record times.

4

Calculate and print the distance

Calculate the distance in centimeters by multiplying pulse_duration by 17150. Then print the distance rounded to 2 decimal places using print(f"Distance: {distance:.2f} cm"). Finally, clean up the GPIO pins with GPIO.cleanup().

Raspberry Pi

import RPi.GPIO as GPIO
import time

TRIG = 23
ECHO = 24

GPIO.setmode(GPIO.BCM)
GPIO.setup(TRIG, GPIO.OUT)
GPIO.setup(ECHO, GPIO.IN)

GPIO.output(TRIG, False)
time.sleep(0.5)

GPIO.output(TRIG, True)
time.sleep(0.00001)
GPIO.output(TRIG, False)

while GPIO.input(ECHO) == 0:
    start = time.time()

while GPIO.input(ECHO) == 1:
    end = time.time()

pulse_duration = end - start

# Calculate distance and print
# Your code here

Need a hint?

Multiply the pulse duration by 17150 to get centimeters. Use an f-string to print with 2 decimals. Always clean up GPIO pins at the end.